New coral study in Tahiti sheds more light on global warming tipping points

Sea ice remnants linger on the shore of Dundee Island, near the Antarctic Peninsula. PHOTO BY BOB BERWYN.

By Summit Voice

SUMMIT COUNTY — Historically, climate change has generally proceeded on a geologic time scale, with small and incremental changes that would be hard to discern on a year-to-year basis.

But during certain periods of rapid transition — between glacial and interglacial periods, for example, the whole system speeds up. One such event occurred about 14,600 years ago, as the world emerged from an ice age.

After closely studying coral reefs in Tahiti, a team of international researchers say a dramatic rise in sea level during what’s known as the Bølling warming corresponds to a rapid collapse of massive ice sheets.

But in a classic chicken-or-egg question, the researchers aren’t sure whether the freshwater pulse was a result of an already warming word or helped to warm the climate.

“Insights into past sea-level changes may help to better constrain future changes. Our work sheds light onto an extreme event of rise in global sea levels in which ice-sheet collapse coincided with a rapid warming,” said researcher Pierre Deschamps. “However, our finding will help scientists currently modelling future climate change scenarios to factor in the dynamic behavior of major ice sheets and finally to provide more reliable predictions of ice sheet responses to a warming climate,” Deschamp said.

“Corals are outstanding archives to reconstruct past sea-level changes as they can be dated to within plus or minus 30 years stretching back thousands of years,” he added. “Moreover, Tahitian reefs are ideally located to reconstruct the deglacial sea-level rise and to constrain short-term events that are thought to have punctuated the period between the Last Glacial Maximum and the present days.

“Tahiti is located at a sufficiently considerable distance from the major former ice sheets to give us close to the average of sea levels across the globe, as a non-volcanic island it is also subsiding into the ocean at a steady pace that we can easily adjust for,” Deschamps said.

The research, published in a recent edition of Nature, suggests that most of the melting water that contributed to the sudden rise in sea level came from the Antarctic ice sheet, highlighting dynamic behavior of this ice sheet in the past.

The authors said more research is needed using cored fossilized corals to better understand the sequence of events related to ice sheet collapse during the last deglaciation.

Today, half of world’s population, approximately 3.2 billion people, lives within 200 km of coastline, and a tenth of the population lives less than 10 meters above sea level. Tahiti itself is, of course, at risk from modern sea-level rise.